Certificate Transparency: Add STH Fetching capability.

components/certificate_transparency/BUILD.gn

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-source_set("filename_util") {
+static_library("certificate_transparency") {
   sources = [
-    "filename_util.cc",
-    "filename_util.h",
+    "log_proof_fetcher.cc",
+    "log_proof_fetcher.h",
   ]
 
   deps = [
     "//base",
-    "//url",
+    "//components/safe_json",
+    "//content",
+    "//net",
   ]
 }